The present invention generally relates to a fuel pump for an internal combustion engine. More specifically, the present invention relates to a high pressure fuel pump cooled by bypass and leakage flows, either individually or in combination.
In low pressure applications, such as conventional port fuel injection gasoline engines on the order of 40-60 psi, fuel pumps typically route the fuel that is being pumped through the center of the pump motor to cool the motor and bearing of the pump. While this works very well at low pressures, direct injection engines require fuel to be delivered at higher pressures, on the order of 300 psi, as described in related provisional application Ser. No. 60/352,434, filed Jan. 28, 2002. The motor housing of a conventional high pressure fuel pump is not adapted to withstand the pressures produced by the high pressure fuel pump. Therefore, in a high pressure fuel pump, the fuel being delivered cannot be routed through the motor to provide cooling of the motor and the bearings. Therefore, there is a need for a high pressure fuel pump that provides a low pressure supply of fuel through the motor to cool the motor and bearings of the high pressure fuel pump.